diff --git a/flow/layers/performance_overlay_layer_unittests.cc b/flow/layers/performance_overlay_layer_unittests.cc
index ecc400c26af74..be49685a99496 100644
--- a/flow/layers/performance_overlay_layer_unittests.cc
+++ b/flow/layers/performance_overlay_layer_unittests.cc
@@ -86,9 +86,9 @@ static void TestPerformanceOverlayLayerGold(int refresh_rate) {
 
   // TODO(https://github.com/flutter/flutter/issues/53784): enable this on all
   // platforms.
-#if !defined(OS_LINUX)
+#if !defined(FML_OS_LINUX)
   GTEST_SKIP() << "Skipping golden tests on non-Linux OSes";
-#endif  // OS_LINUX
+#endif  // FML_OS_LINUX
   const bool golden_data_matches = golden_data->equals(snapshot_data.get());
   if (!golden_data_matches) {
     SkFILEWStream wstream(new_golden_file_path.c_str());
diff --git a/fml/build_config.h b/fml/build_config.h
index 2714f46d1cebf..256201614d467 100644
--- a/fml/build_config.h
+++ b/fml/build_config.h
@@ -4,13 +4,14 @@
 
 // This file adds defines about the platform we're currently building on.
 //  Operating System:
-//    OS_WIN / OS_MACOSX / OS_LINUX / OS_POSIX (MACOSX or LINUX) /
-//    OS_NACL (NACL_SFI or NACL_NONSFI) / OS_NACL_SFI / OS_NACL_NONSFI
+//    OS_WIN / FML_OS_MACOSX / FML_OS_LINUX / FML_OS_POSIX (MACOSX or LINUX) /
+//    FML_OS_NACL (NACL_SFI or NACL_NONSFI) / FML_OS_NACL_SFI /
+//    FML_OS_NACL_NONSFI
 //  Compiler:
 //    COMPILER_MSVC / COMPILER_GCC
 //  Processor:
-//    ARCH_CPU_X86 / ARCH_CPU_X86_64 / ARCH_CPU_X86_FAMILY (X86 or X86_64)
-//    ARCH_CPU_32_BITS / ARCH_CPU_64_BITS
+//    FML_ARCH_CPU_X86 / FML_ARCH_CPU_X86_64 / FML_ARCH_CPU_X86_FAMILY (X86 or
+//    X86_64) FML_ARCH_CPU_32_BITS / FML_ARCH_CPU_64_BITS
 
 #ifndef FLUTTER_FML_BUILD_CONFIG_H_
 #define FLUTTER_FML_BUILD_CONFIG_H_
@@ -18,18 +19,18 @@
 #if defined(__Fuchsia__)
 #define OS_FUCHSIA 1
 #elif defined(ANDROID)
-#define OS_ANDROID 1
+#define FML_OS_ANDROID 1
 #elif defined(__APPLE__)
 // only include TargetConditions after testing ANDROID as some android builds
 // on mac don't have this header available and it's not needed unless the target
 // is really mac/ios.
 #include <TargetConditionals.h>
-#define OS_MACOSX 1
+#define FML_OS_MACOSX 1
 #if defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE
 #define OS_IOS 1
 #endif  // defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE
 #elif defined(__linux__)
-#define OS_LINUX 1
+#define FML_OS_LINUX 1
 // include a system header to pull in features.h for glibc/uclibc macros.
 #include <unistd.h>
 #if defined(__GLIBC__) && !defined(__UCLIBC__)
@@ -39,29 +40,30 @@
 #elif defined(_WIN32)
 #define OS_WIN 1
 #elif defined(__FreeBSD__)
-#define OS_FREEBSD 1
+#define FML_OS_FREEBSD 1
 #elif defined(__OpenBSD__)
-#define OS_OPENBSD 1
+#define FML_OS_OPENBSD 1
 #elif defined(__sun)
-#define OS_SOLARIS 1
+#define FML_OS_SOLARIS 1
 #elif defined(__QNXNTO__)
-#define OS_QNX 1
+#define FML_OS_QNX 1
 #else
 #error Please add support for your platform in flutter/fml/build_config.h
 #endif
 
 // For access to standard BSD features, use OS_BSD instead of a
 // more specific macro.
-#if defined(OS_FREEBSD) || defined(OS_OPENBSD)
+#if defined(FML_OS_FREEBSD) || defined(FML_OS_OPENBSD)
 #define OS_BSD 1
 #endif
 
-// For access to standard POSIXish features, use OS_POSIX instead of a
+// For access to standard POSIXish features, use FML_OS_POSIX instead of a
 // more specific macro.
-#if defined(OS_MACOSX) || defined(OS_LINUX) || defined(OS_FREEBSD) ||    \
-    defined(OS_OPENBSD) || defined(OS_SOLARIS) || defined(OS_ANDROID) || \
-    defined(OS_NACL) || defined(OS_QNX)
-#define OS_POSIX 1
+#if defined(FML_OS_MACOSX) || defined(FML_OS_LINUX) ||    \
+    defined(FML_OS_FREEBSD) || defined(FML_OS_OPENBSD) || \
+    defined(FML_OS_SOLARIS) || defined(FML_OS_ANDROID) || \
+    defined(FML_OS_NACL) || defined(FML_OS_QNX)
+#define FML_OS_POSIX 1
 #endif
 
 // Processor architecture detection.  For more info on what's defined, see:
@@ -69,40 +71,28 @@
 //   http://www.agner.org/optimize/calling_conventions.pdf
 //   or with gcc, run: "echo | gcc -E -dM -"
 #if defined(_M_X64) || defined(__x86_64__)
-#define ARCH_CPU_X86_FAMILY 1
-#define ARCH_CPU_X86_64 1
-#define ARCH_CPU_64_BITS 1
-#define ARCH_CPU_LITTLE_ENDIAN 1
+#define FML_ARCH_CPU_X86_FAMILY 1
+#define FML_ARCH_CPU_X86_64 1
+#define FML_ARCH_CPU_64_BITS 1
+#define FML_ARCH_CPU_LITTLE_ENDIAN 1
 #elif defined(_M_IX86) || defined(__i386__)
-#define ARCH_CPU_X86_FAMILY 1
-#define ARCH_CPU_X86 1
-#define ARCH_CPU_32_BITS 1
-#define ARCH_CPU_LITTLE_ENDIAN 1
+#define FML_ARCH_CPU_X86_FAMILY 1
+#define FML_ARCH_CPU_X86 1
+#define FML_ARCH_CPU_32_BITS 1
+#define FML_ARCH_CPU_LITTLE_ENDIAN 1
 #elif defined(__ARMEL__)
-#define ARCH_CPU_ARM_FAMILY 1
-#define ARCH_CPU_ARMEL 1
-#define ARCH_CPU_32_BITS 1
-#define ARCH_CPU_LITTLE_ENDIAN 1
+#define FML_ARCH_CPU_ARM_FAMILY 1
+#define FML_ARCH_CPU_ARMEL 1
+#define FML_ARCH_CPU_32_BITS 1
+#define FML_ARCH_CPU_LITTLE_ENDIAN 1
 #elif defined(__aarch64__)
-#define ARCH_CPU_ARM_FAMILY 1
-#define ARCH_CPU_ARM64 1
-#define ARCH_CPU_64_BITS 1
-#define ARCH_CPU_LITTLE_ENDIAN 1
+#define FML_ARCH_CPU_ARM_FAMILY 1
+#define FML_ARCH_CPU_ARM64 1
+#define FML_ARCH_CPU_64_BITS 1
+#define FML_ARCH_CPU_LITTLE_ENDIAN 1
 #elif defined(__pnacl__)
-#define ARCH_CPU_32_BITS 1
-#define ARCH_CPU_LITTLE_ENDIAN 1
-#elif defined(__MIPSEL__)
-#if defined(__LP64__)
-#define ARCH_CPU_MIPS64_FAMILY 1
-#define ARCH_CPU_MIPS64EL 1
-#define ARCH_CPU_64_BITS 1
-#define ARCH_CPU_LITTLE_ENDIAN 1
-#else
-#define ARCH_CPU_MIPS_FAMILY 1
-#define ARCH_CPU_MIPSEL 1
-#define ARCH_CPU_32_BITS 1
-#define ARCH_CPU_LITTLE_ENDIAN 1
-#endif
+#define FML_ARCH_CPU_32_BITS 1
+#define FML_ARCH_CPU_LITTLE_ENDIAN 1
 #else
 #error Please add support for your architecture in flutter/fml/build_config.h
 #endif
diff --git a/fml/endianness.h b/fml/endianness.h
index 4951f7c2edeaf..b4bd9a9b2d42d 100644
--- a/fml/endianness.h
+++ b/fml/endianness.h
@@ -49,7 +49,7 @@ constexpr T ByteSwap(T n) {
 ///         The given value must be an integral type of size 1, 2, 4, or 8.
 template <typename T, class = std::enable_if_t<std::is_integral_v<T>>>
 constexpr T BigEndianToArch(T n) {
-#if ARCH_CPU_LITTLE_ENDIAN
+#if FML_ARCH_CPU_LITTLE_ENDIAN
   return ByteSwap<T>(n);
 #else
   return n;
@@ -61,7 +61,7 @@ constexpr T BigEndianToArch(T n) {
 ///         The given value must be an integral type of size 1, 2, 4, or 8.
 template <typename T, class = std::enable_if_t<std::is_integral_v<T>>>
 constexpr T LittleEndianToArch(T n) {
-#if !ARCH_CPU_LITTLE_ENDIAN
+#if !FML_ARCH_CPU_LITTLE_ENDIAN
   return ByteSwap<T>(n);
 #else
   return n;
diff --git a/fml/endianness_unittests.cc b/fml/endianness_unittests.cc
index 24b35464e82bd..1523661174304 100644
--- a/fml/endianness_unittests.cc
+++ b/fml/endianness_unittests.cc
@@ -16,7 +16,7 @@ TEST(EndiannessTest, ByteSwap) {
 }
 
 TEST(EndiannessTest, BigEndianToArch) {
-#if ARCH_CPU_LITTLE_ENDIAN
+#if FML_ARCH_CPU_LITTLE_ENDIAN
   uint32_t expected = 0x44332211;
 #else
   uint32_t expected = 0x11223344;
@@ -25,7 +25,7 @@ TEST(EndiannessTest, BigEndianToArch) {
 }
 
 TEST(EndiannessTest, LittleEndianToArch) {
-#if ARCH_CPU_LITTLE_ENDIAN
+#if FML_ARCH_CPU_LITTLE_ENDIAN
   uint32_t expected = 0x11223344;
 #else
   uint32_t expected = 0x44332211;
diff --git a/fml/logging.cc b/fml/logging.cc
index e3a57df4bbccc..5830cb79c2624 100644
--- a/fml/logging.cc
+++ b/fml/logging.cc
@@ -9,7 +9,7 @@
 #include "flutter/fml/log_settings.h"
 #include "flutter/fml/logging.h"
 
-#if defined(OS_ANDROID)
+#if defined(FML_OS_ANDROID)
 #include <android/log.h>
 #elif defined(OS_IOS)
 #include <syslog.h>
@@ -76,7 +76,7 @@ LogMessage::~LogMessage() {
   stream_ << std::endl;
 #endif
 
-#if defined(OS_ANDROID)
+#if defined(FML_OS_ANDROID)
   android_LogPriority priority =
       (severity_ < 0) ? ANDROID_LOG_VERBOSE : ANDROID_LOG_UNKNOWN;
   switch (severity_) {
diff --git a/fml/message_loop_impl.cc b/fml/message_loop_impl.cc
index a206b11a74f22..ca47c0964e896 100644
--- a/fml/message_loop_impl.cc
+++ b/fml/message_loop_impl.cc
@@ -13,13 +13,13 @@
 #include "flutter/fml/logging.h"
 #include "flutter/fml/trace_event.h"
 
-#if OS_MACOSX
+#if FML_OS_MACOSX
 #include "flutter/fml/platform/darwin/message_loop_darwin.h"
-#elif OS_ANDROID
+#elif FML_OS_ANDROID
 #include "flutter/fml/platform/android/message_loop_android.h"
 #elif OS_FUCHSIA
 #include "flutter/fml/platform/fuchsia/message_loop_fuchsia.h"
-#elif OS_LINUX
+#elif FML_OS_LINUX
 #include "flutter/fml/platform/linux/message_loop_linux.h"
 #elif OS_WIN
 #include "flutter/fml/platform/win/message_loop_win.h"
@@ -28,13 +28,13 @@
 namespace fml {
 
 fml::RefPtr<MessageLoopImpl> MessageLoopImpl::Create() {
-#if OS_MACOSX
+#if FML_OS_MACOSX
   return fml::MakeRefCounted<MessageLoopDarwin>();
-#elif OS_ANDROID
+#elif FML_OS_ANDROID
   return fml::MakeRefCounted<MessageLoopAndroid>();
 #elif OS_FUCHSIA
   return fml::MakeRefCounted<MessageLoopFuchsia>();
-#elif OS_LINUX
+#elif FML_OS_LINUX
   return fml::MakeRefCounted<MessageLoopLinux>();
 #elif OS_WIN
   return fml::MakeRefCounted<MessageLoopWin>();
diff --git a/fml/synchronization/semaphore.cc b/fml/synchronization/semaphore.cc
index 7156e2ec88171..c28a57d632c3a 100644
--- a/fml/synchronization/semaphore.cc
+++ b/fml/synchronization/semaphore.cc
@@ -7,7 +7,7 @@
 #include "flutter/fml/build_config.h"
 #include "flutter/fml/logging.h"
 
-#if OS_MACOSX
+#if FML_OS_MACOSX
 #include <dispatch/dispatch.h>
 
 namespace fml {
diff --git a/fml/thread.cc b/fml/thread.cc
index 5eb05deaf978a..7a5e951da1621 100644
--- a/fml/thread.cc
+++ b/fml/thread.cc
@@ -71,9 +71,9 @@ void Thread::SetCurrentThreadName(const std::string& name) {
   if (name == "") {
     return;
   }
-#if defined(OS_MACOSX)
+#if defined(FML_OS_MACOSX)
   pthread_setname_np(name.c_str());
-#elif defined(OS_LINUX) || defined(OS_ANDROID)
+#elif defined(FML_OS_LINUX) || defined(FML_OS_ANDROID)
   pthread_setname_np(pthread_self(), name.c_str());
 #elif defined(OS_WIN)
   THREADNAME_INFO info;
diff --git a/fml/thread_local.h b/fml/thread_local.h
index ed6336c961554..010c0ff643dd3 100644
--- a/fml/thread_local.h
+++ b/fml/thread_local.h
@@ -10,7 +10,8 @@
 #include "flutter/fml/build_config.h"
 #include "flutter/fml/macros.h"
 
-#define FML_THREAD_LOCAL_PTHREADS OS_MACOSX || OS_LINUX || OS_ANDROID
+#define FML_THREAD_LOCAL_PTHREADS \
+  FML_OS_MACOSX || FML_OS_LINUX || FML_OS_ANDROID
 
 #if FML_THREAD_LOCAL_PTHREADS
 #include <pthread.h>
diff --git a/fml/trace_event.h b/fml/trace_event.h
index 38a3ea2a9b225..d89e421a7bec6 100644
--- a/fml/trace_event.h
+++ b/fml/trace_event.h
@@ -47,7 +47,7 @@
 #include "flutter/fml/time/time_point.h"
 #include "third_party/dart/runtime/include/dart_tools_api.h"
 
-#if (FLUTTER_RELEASE && !defined(OS_FUCHSIA) && !defined(OS_ANDROID))
+#if (FLUTTER_RELEASE && !defined(OS_FUCHSIA) && !defined(FML_OS_ANDROID))
 #define FLUTTER_TIMELINE_ENABLED 0
 #else
 #define FLUTTER_TIMELINE_ENABLED 1
diff --git a/lib/ui/painting/image_generator_registry.cc b/lib/ui/painting/image_generator_registry.cc
index 3d5d4cf5ecb98..0fc40010f2f6b 100644
--- a/lib/ui/painting/image_generator_registry.cc
+++ b/lib/ui/painting/image_generator_registry.cc
@@ -8,7 +8,7 @@
 #include "third_party/skia/include/codec/SkCodec.h"
 #include "third_party/skia/include/core/SkImageGenerator.h"
 #include "third_party/skia/src/codec/SkCodecImageGenerator.h"
-#ifdef OS_MACOSX
+#ifdef FML_OS_MACOSX
 #include "third_party/skia/include/ports/SkImageGeneratorCG.h"
 #elif OS_WIN
 #include "third_party/skia/include/ports/SkImageGeneratorWIC.h"
@@ -24,7 +24,7 @@ ImageGeneratorRegistry::ImageGeneratorRegistry() : weak_factory_(this) {
       0);
 
   // todo(bdero): https://github.com/flutter/flutter/issues/82603
-#ifdef OS_MACOSX
+#ifdef FML_OS_MACOSX
   AddFactory(
       [](sk_sp<SkData> buffer) {
         auto generator = SkImageGeneratorCG::MakeFromEncodedCG(buffer);
diff --git a/lib/ui/painting/immutable_buffer.cc b/lib/ui/painting/immutable_buffer.cc
index 6491785f6eae0..e4d3f630de72f 100644
--- a/lib/ui/painting/immutable_buffer.cc
+++ b/lib/ui/painting/immutable_buffer.cc
@@ -11,7 +11,7 @@
 #include "third_party/tonic/dart_args.h"
 #include "third_party/tonic/dart_binding_macros.h"
 
-#if OS_ANDROID
+#if FML_OS_ANDROID
 #include <sys/mman.h>
 #endif
 
@@ -53,7 +53,7 @@ size_t ImmutableBuffer::GetAllocationSize() const {
   return sizeof(ImmutableBuffer) + data_->size();
 }
 
-#if OS_ANDROID
+#if FML_OS_ANDROID
 
 // Compressed image buffers are allocated on the UI thread but are deleted on a
 // decoder worker thread.  Android's implementation of malloc appears to
@@ -96,6 +96,6 @@ sk_sp<SkData> ImmutableBuffer::MakeSkDataWithCopy(const void* data,
   return SkData::MakeWithCopy(data, length);
 }
 
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 
 }  // namespace flutter
diff --git a/lib/ui/ui_dart_state.cc b/lib/ui/ui_dart_state.cc
index 06411c4d3ce98..0aac768d61167 100644
--- a/lib/ui/ui_dart_state.cc
+++ b/lib/ui/ui_dart_state.cc
@@ -11,7 +11,7 @@
 #include "third_party/tonic/converter/dart_converter.h"
 #include "third_party/tonic/dart_message_handler.h"
 
-#if defined(OS_ANDROID)
+#if defined(FML_OS_ANDROID)
 #include <android/log.h>
 #elif defined(OS_IOS)
 extern "C" {
@@ -216,7 +216,7 @@ void UIDartState::LogMessage(const std::string& tag,
     log_message_callback_(tag, message);
   } else {
     // Fall back to previous behavior if unspecified.
-#if defined(OS_ANDROID)
+#if defined(FML_OS_ANDROID)
     __android_log_print(ANDROID_LOG_INFO, tag.c_str(), "%.*s",
                         (int)message.size(), message.c_str());
 #elif defined(OS_IOS)
diff --git a/runtime/dart_snapshot.cc b/runtime/dart_snapshot.cc
index e567dd58d41bc..b875cbc48d2b7 100644
--- a/runtime/dart_snapshot.cc
+++ b/runtime/dart_snapshot.cc
@@ -25,7 +25,7 @@ const char* DartSnapshot::kIsolateInstructionsSymbol =
 // data through symbols that are statically linked into the executable.
 // On other platforms this data is obtained by a dynamic symbol lookup.
 #define DART_SNAPSHOT_STATIC_LINK \
-  ((OS_WIN || OS_ANDROID) && FLUTTER_JIT_RUNTIME)
+  ((OS_WIN || FML_OS_ANDROID) && FLUTTER_JIT_RUNTIME)
 
 #if !DART_SNAPSHOT_STATIC_LINK
 
diff --git a/runtime/dart_vm.cc b/runtime/dart_vm.cc
index ad3612b14305e..77bf094e960a3 100644
--- a/runtime/dart_vm.cc
+++ b/runtime/dart_vm.cc
@@ -221,7 +221,7 @@ static std::vector<const char*> ProfilingFlags(bool enable_profiling) {
           // This instructs the profiler to walk C++ frames, and to include
           // them in the profile.
           "--profile-vm",
-#if OS_IOS && ARCH_CPU_ARM_FAMILY && ARCH_CPU_ARMEL
+#if OS_IOS && FML_ARCH_CPU_ARM_FAMILY && FML_ARCH_CPU_ARMEL
           // Set the profiler interrupt period to 500Hz instead of the
           // default 1000Hz on 32-bit iOS devices to reduce average and worst
           // case frame build times.
@@ -232,7 +232,7 @@ static std::vector<const char*> ProfilingFlags(bool enable_profiling) {
           "--profile_period=2000",
 #else
           "--profile_period=1000",
-#endif  // OS_IOS && ARCH_CPU_ARM_FAMILY && ARCH_CPU_ARMEL
+#endif  // OS_IOS && FML_ARCH_CPU_ARM_FAMILY && FML_ARCH_CPU_ARMEL
     };
   } else {
     return {"--no-profiler"};
@@ -341,7 +341,7 @@ DartVM::DartVM(std::shared_ptr<const DartVMData> vm_data,
 #endif  // !OS_FUCHSIA
 
 #if (FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG)
-#if !OS_IOS && !OS_MACOSX
+#if !OS_IOS && !FML_OS_MACOSX
   // Debug mode uses the JIT, disable code page write protection to avoid
   // memory page protection changes before and after every compilation.
   PushBackAll(&args, kDartWriteProtectCodeArgs,
@@ -361,7 +361,7 @@ DartVM::DartVM(std::shared_ptr<const DartVMData> vm_data,
   PushBackAll(&args, kDartDisableIntegerDivisionArgs,
               fml::size(kDartDisableIntegerDivisionArgs));
 #endif  // TARGET_CPU_ARM
-#endif  // !OS_IOS && !OS_MACOSX
+#endif  // !OS_IOS && !FML_OS_MACOSX
 #endif  // (FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG)
 
   if (enable_asserts) {
diff --git a/shell/common/switches.cc b/shell/common/switches.cc
index 29bc3d5e9e269..7f507b0786b75 100644
--- a/shell/common/switches.cc
+++ b/shell/common/switches.cc
@@ -79,7 +79,7 @@ static const std::string gAllowedDartFlags[] = {
 // Define symbols for the ICU data that is linked into the Flutter library on
 // Android.  This is a workaround for crashes seen when doing dynamic lookups
 // of the engine's own symbols on some older versions of Android.
-#if OS_ANDROID
+#if FML_OS_ANDROID
 extern uint8_t _binary_icudtl_dat_start[];
 extern uint8_t _binary_icudtl_dat_end[];
 
@@ -401,7 +401,7 @@ Settings SettingsFromCommandLine(const fml::CommandLine& command_line) {
       command_line.GetOptionValue(FlagForSwitch(Switch::ICUNativeLibPath),
                                   &native_lib_path);
 
-#if OS_ANDROID
+#if FML_OS_ANDROID
       settings.icu_mapper = GetICUStaticMapping;
 #else
       settings.icu_mapper = [icu_symbol_prefix, native_lib_path] {
diff --git a/shell/platform/android/jni/platform_view_android_jni.h b/shell/platform/android/jni/platform_view_android_jni.h
index cb838b2c200df..8e38a385fe771 100644
--- a/shell/platform/android/jni/platform_view_android_jni.h
+++ b/shell/platform/android/jni/platform_view_android_jni.h
@@ -13,13 +13,13 @@
 #include "flutter/shell/platform/android/surface/android_native_window.h"
 #include "third_party/skia/include/core/SkMatrix.h"
 
-#if OS_ANDROID
+#if FML_OS_ANDROID
 #include "flutter/fml/platform/android/scoped_java_ref.h"
 #endif
 
 namespace flutter {
 
-#if OS_ANDROID
+#if FML_OS_ANDROID
 using JavaLocalRef = fml::jni::ScopedJavaLocalRef<jobject>;
 #else
 using JavaLocalRef = std::nullptr_t;
diff --git a/shell/platform/android/surface/android_native_window.cc b/shell/platform/android/surface/android_native_window.cc
index 5e4ebef7840b5..20e75f57aaf58 100644
--- a/shell/platform/android/surface/android_native_window.cc
+++ b/shell/platform/android/surface/android_native_window.cc
@@ -14,9 +14,9 @@ AndroidNativeWindow::AndroidNativeWindow(Handle window)
 
 AndroidNativeWindow::~AndroidNativeWindow() {
   if (window_ != nullptr) {
-#if OS_ANDROID
+#if FML_OS_ANDROID
     ANativeWindow_release(window_);
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
     window_ = nullptr;
   }
 }
@@ -30,13 +30,13 @@ AndroidNativeWindow::Handle AndroidNativeWindow::handle() const {
 }
 
 SkISize AndroidNativeWindow::GetSize() const {
-#if OS_ANDROID
+#if FML_OS_ANDROID
   return window_ == nullptr ? SkISize::Make(0, 0)
                             : SkISize::Make(ANativeWindow_getWidth(window_),
                                             ANativeWindow_getHeight(window_));
-#else   // OS_ANDROID
+#else   // FML_OS_ANDROID
   return SkISize::Make(0, 0);
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 }
 
 }  // namespace flutter
diff --git a/shell/platform/android/surface/android_native_window.h b/shell/platform/android/surface/android_native_window.h
index ac684b955eb4b..633ee02fadc13 100644
--- a/shell/platform/android/surface/android_native_window.h
+++ b/shell/platform/android/surface/android_native_window.h
@@ -11,20 +11,20 @@
 #include "flutter/fml/memory/ref_counted.h"
 #include "third_party/skia/include/core/SkSize.h"
 
-#if OS_ANDROID
+#if FML_OS_ANDROID
 #include <android/native_window.h>
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 
 namespace flutter {
 
 class AndroidNativeWindow
     : public fml::RefCountedThreadSafe<AndroidNativeWindow> {
  public:
-#if OS_ANDROID
+#if FML_OS_ANDROID
   using Handle = ANativeWindow*;
-#else   // OS_ANDROID
+#else   // FML_OS_ANDROID
   using Handle = std::nullptr_t;
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 
   bool IsValid() const;
 
diff --git a/shell/platform/embedder/embedder.cc b/shell/platform/embedder/embedder.cc
index c08651e6f3973..a4850e3f64909 100644
--- a/shell/platform/embedder/embedder.cc
+++ b/shell/platform/embedder/embedder.cc
@@ -183,18 +183,18 @@ static bool IsRendererValid(const FlutterRendererConfig* config) {
   return false;
 }
 
-#if OS_LINUX || OS_WIN
+#if FML_OS_LINUX || OS_WIN
 static void* DefaultGLProcResolver(const char* name) {
   static fml::RefPtr<fml::NativeLibrary> proc_library =
-#if OS_LINUX
+#if FML_OS_LINUX
       fml::NativeLibrary::CreateForCurrentProcess();
-#elif OS_WIN  // OS_LINUX
+#elif OS_WIN  // FML_OS_LINUX
       fml::NativeLibrary::Create("opengl32.dll");
 #endif        // OS_WIN
   return static_cast<void*>(
       const_cast<uint8_t*>(proc_library->ResolveSymbol(name)));
 }
-#endif  // OS_LINUX || OS_WIN
+#endif  // FML_OS_LINUX || OS_WIN
 
 static flutter::Shell::CreateCallback<flutter::PlatformView>
 InferOpenGLPlatformViewCreationCallback(
@@ -284,7 +284,7 @@ InferOpenGLPlatformViewCreationCallback(
       return ptr(user_data, gl_proc_name);
     };
   } else {
-#if OS_LINUX || OS_WIN
+#if FML_OS_LINUX || OS_WIN
     gl_proc_resolver = DefaultGLProcResolver;
 #endif
   }
@@ -887,7 +887,8 @@ void PopulateSnapshotMappingCallbacks(
 #if !OS_FUCHSIA && (FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG)
   settings.dart_library_sources_kernel =
       make_mapping_callback(kPlatformStrongDill, kPlatformStrongDillSize);
-#endif  // !OS_FUCHSIA && (FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG)
+#endif  // !OS_FUCHSIA && (FLUTTER_RUNTIME_MODE ==
+        // FLUTTER_RUNTIME_MODE_DEBUG)
 }
 
 FlutterEngineResult FlutterEngineRun(size_t version,
diff --git a/shell/platform/embedder/tests/embedder_unittests.cc b/shell/platform/embedder/tests/embedder_unittests.cc
index 3108cff91e200..5dccfab382910 100644
--- a/shell/platform/embedder/tests/embedder_unittests.cc
+++ b/shell/platform/embedder/tests/embedder_unittests.cc
@@ -1028,9 +1028,9 @@ TEST_F(EmbedderTest, VerifyB143464703WithSoftwareBackend) {
 
   // TODO(https://github.com/flutter/flutter/issues/53784): enable this on all
   // platforms.
-#if !defined(OS_LINUX)
+#if !defined(FML_OS_LINUX)
   GTEST_SKIP() << "Skipping golden tests on non-Linux OSes";
-#endif  // OS_LINUX
+#endif  // FML_OS_LINUX
   ASSERT_TRUE(
       ImageMatchesFixture("verifyb143464703_soft_noxform.png", rendered_scene));
 }
diff --git a/shell/testing/tester_main.cc b/shell/testing/tester_main.cc
index b96166c5faee6..b059908416b78 100644
--- a/shell/testing/tester_main.cc
+++ b/shell/testing/tester_main.cc
@@ -27,9 +27,9 @@
 #include "third_party/dart/runtime/include/bin/dart_io_api.h"
 #include "third_party/dart/runtime/include/dart_api.h"
 
-#if defined(OS_POSIX)
+#if defined(FML_OS_POSIX)
 #include <signal.h>
-#endif  // defined(OS_POSIX)
+#endif  // defined(FML_OS_POSIX)
 
 namespace flutter {
 
@@ -169,12 +169,12 @@ class ScriptCompletionTaskObserver {
 // mutator thread in the main isolate in this process (threads spawned by the VM
 // know about this limitation and automatically have this signal unblocked).
 static void UnblockSIGPROF() {
-#if defined(OS_POSIX)
+#if defined(FML_OS_POSIX)
   sigset_t set;
   sigemptyset(&set);
   sigaddset(&set, SIGPROF);
   pthread_sigmask(SIG_UNBLOCK, &set, NULL);
-#endif  // defined(OS_POSIX)
+#endif  // defined(FML_OS_POSIX)
 }
 
 int RunTester(const flutter::Settings& settings,
diff --git a/testing/dart_fixture.cc b/testing/dart_fixture.cc
index 2852f4165fb54..0f92085406098 100644
--- a/testing/dart_fixture.cc
+++ b/testing/dart_fixture.cc
@@ -49,10 +49,10 @@ void DartFixture::SetSnapshotsAndAssets(Settings& settings) {
   // snapshots will be present in the application AOT dylib.
   if (DartVM::IsRunningPrecompiledCode()) {
     FML_CHECK(PrepareSettingsForAOTWithSymbols(settings, aot_symbols_));
-#if OS_LINUX
+#if FML_OS_LINUX
     settings.vmservice_snapshot_library_path.emplace_back(fml::paths::JoinPaths(
         {GetTestingAssetsPath(), "libvmservice_snapshot.so"}));
-#endif  // OS_LINUX
+#endif  // FML_OS_LINUX
   } else {
     settings.application_kernels = [this]() -> Mappings {
       std::vector<std::unique_ptr<const fml::Mapping>> kernel_mappings;
diff --git a/testing/debugger_detection.cc b/testing/debugger_detection.cc
index 91a51ee3e8e0d..8ce2321763eac 100644
--- a/testing/debugger_detection.cc
+++ b/testing/debugger_detection.cc
@@ -7,13 +7,13 @@
 #include "flutter/fml/build_config.h"
 #include "flutter/fml/logging.h"
 
-#if OS_MACOSX
+#if FML_OS_MACOSX
 #include <assert.h>
 #include <stdbool.h>
 #include <sys/sysctl.h>
 #include <sys/types.h>
 #include <unistd.h>
-#endif  // OS_MACOSX
+#endif  // FML_OS_MACOSX
 
 #if OS_WIN
 #include <windows.h>
@@ -23,7 +23,7 @@ namespace flutter {
 namespace testing {
 
 DebuggerStatus GetDebuggerStatus() {
-#if OS_MACOSX
+#if FML_OS_MACOSX
   // From Technical Q&A QA1361 Detecting the Debugger
   // https://developer.apple.com/library/archive/qa/qa1361/_index.html
   int management_info_base[4];
diff --git a/testing/test_gl_surface.cc b/testing/test_gl_surface.cc
index 36ffe6831a336..8ee71caa26b65 100644
--- a/testing/test_gl_surface.cc
+++ b/testing/test_gl_surface.cc
@@ -298,7 +298,7 @@ sk_sp<SkSurface> TestGLSurface::GetOnscreenSurface() {
   const uint32_t width = surface_size_.width();
   const uint32_t height = surface_size_.height();
   framebuffer_info.fFBOID = GetFramebuffer(width, height);
-#if OS_MACOSX
+#if FML_OS_MACOSX
   framebuffer_info.fFormat = GR_GL_RGBA8;
 #else
   framebuffer_info.fFormat = GR_GL_BGRA8;
diff --git a/testing/test_vulkan_context.cc b/testing/test_vulkan_context.cc
index ab83100982055..73df59d813104 100644
--- a/testing/test_vulkan_context.cc
+++ b/testing/test_vulkan_context.cc
@@ -6,7 +6,7 @@
 
 #include "flutter/vulkan/vulkan_proc_table.h"
 
-#ifdef OS_MACOSX
+#ifdef FML_OS_MACOSX
 #define VULKAN_SO_PATH "libvk_swiftshader.dylib"
 #elif OS_WIN
 #define VULKAN_SO_PATH "vk_swiftshader.dll"
diff --git a/vulkan/vulkan_device.cc b/vulkan/vulkan_device.cc
index c4a8d334b9102..e981329d2174b 100644
--- a/vulkan/vulkan_device.cc
+++ b/vulkan/vulkan_device.cc
@@ -60,7 +60,7 @@ VulkanDevice::VulkanDevice(VulkanProcTable& p_vk,
   };
 
   const char* extensions[] = {
-#if OS_ANDROID
+#if FML_OS_ANDROID
     VK_KHR_SWAPCHAIN_EXTENSION_NAME,
 #endif
 #if OS_FUCHSIA
@@ -185,7 +185,7 @@ uint32_t VulkanDevice::GetGraphicsQueueIndex() const {
 bool VulkanDevice::GetSurfaceCapabilities(
     const VulkanSurface& surface,
     VkSurfaceCapabilitiesKHR* capabilities) const {
-#if OS_ANDROID
+#if FML_OS_ANDROID
   if (!surface.IsValid() || capabilities == nullptr) {
     return false;
   }
@@ -274,7 +274,7 @@ std::vector<VkQueueFamilyProperties> VulkanDevice::GetQueueFamilyProperties()
 int VulkanDevice::ChooseSurfaceFormat(const VulkanSurface& surface,
                                       std::vector<VkFormat> desired_formats,
                                       VkSurfaceFormatKHR* format) const {
-#if OS_ANDROID
+#if FML_OS_ANDROID
   if (!surface.IsValid() || format == nullptr) {
     return -1;
   }
diff --git a/vulkan/vulkan_interface.h b/vulkan/vulkan_interface.h
index e973b5ffafeb6..03218c9621b2a 100644
--- a/vulkan/vulkan_interface.h
+++ b/vulkan/vulkan_interface.h
@@ -10,11 +10,11 @@
 #include "flutter/fml/build_config.h"
 #include "flutter/fml/logging.h"
 
-#if OS_ANDROID
+#if FML_OS_ANDROID
 #ifndef VK_USE_PLATFORM_ANDROID_KHR
 #define VK_USE_PLATFORM_ANDROID_KHR 1
 #endif  // VK_USE_PLATFORM_ANDROID_KHR
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 
 #if OS_FUCHSIA
 #ifndef VK_USE_PLATFORM_MAGMA_KHR
diff --git a/vulkan/vulkan_proc_table.cc b/vulkan/vulkan_proc_table.cc
index d5017e313a382..f5ba8f97bcb3c 100644
--- a/vulkan/vulkan_proc_table.cc
+++ b/vulkan/vulkan_proc_table.cc
@@ -79,14 +79,14 @@ bool VulkanProcTable::SetupInstanceProcAddresses(
   ACQUIRE_PROC(GetDeviceProcAddr, handle);
   ACQUIRE_PROC(GetPhysicalDeviceFeatures, handle);
   ACQUIRE_PROC(GetPhysicalDeviceQueueFamilyProperties, handle);
-#if OS_ANDROID
+#if FML_OS_ANDROID
   ACQUIRE_PROC(GetPhysicalDeviceSurfaceCapabilitiesKHR, handle);
   ACQUIRE_PROC(GetPhysicalDeviceSurfaceFormatsKHR, handle);
   ACQUIRE_PROC(GetPhysicalDeviceSurfacePresentModesKHR, handle);
   ACQUIRE_PROC(GetPhysicalDeviceSurfaceSupportKHR, handle);
   ACQUIRE_PROC(DestroySurfaceKHR, handle);
   ACQUIRE_PROC(CreateAndroidSurfaceKHR, handle);
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 
   // The debug report functions are optional. We don't want proc acquisition to
   // fail here because the optional methods were not present (since ACQUIRE_PROC
@@ -130,13 +130,13 @@ bool VulkanProcTable::SetupDeviceProcAddresses(
   ACQUIRE_PROC(ResetFences, handle);
   ACQUIRE_PROC(WaitForFences, handle);
 #ifndef TEST_VULKAN_PROCS
-#if OS_ANDROID
+#if FML_OS_ANDROID
   ACQUIRE_PROC(AcquireNextImageKHR, handle);
   ACQUIRE_PROC(CreateSwapchainKHR, handle);
   ACQUIRE_PROC(DestroySwapchainKHR, handle);
   ACQUIRE_PROC(GetSwapchainImagesKHR, handle);
   ACQUIRE_PROC(QueuePresentKHR, handle);
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 #if OS_FUCHSIA
   ACQUIRE_PROC(ImportSemaphoreZirconHandleFUCHSIA, handle);
   ACQUIRE_PROC(GetSemaphoreZirconHandleFUCHSIA, handle);
diff --git a/vulkan/vulkan_proc_table.h b/vulkan/vulkan_proc_table.h
index fddb8cfda96d8..a7f2a3d5f35b8 100644
--- a/vulkan/vulkan_proc_table.h
+++ b/vulkan/vulkan_proc_table.h
@@ -107,7 +107,7 @@ class VulkanProcTable : public fml::RefCountedThreadSafe<VulkanProcTable> {
   DEFINE_PROC(ResetFences);
   DEFINE_PROC(WaitForFences);
 #ifndef TEST_VULKAN_PROCS
-#if OS_ANDROID
+#if FML_OS_ANDROID
   DEFINE_PROC(GetPhysicalDeviceSurfaceCapabilitiesKHR);
   DEFINE_PROC(GetPhysicalDeviceSurfaceFormatsKHR);
   DEFINE_PROC(GetPhysicalDeviceSurfacePresentModesKHR);
@@ -115,7 +115,7 @@ class VulkanProcTable : public fml::RefCountedThreadSafe<VulkanProcTable> {
   DEFINE_PROC(GetSwapchainImagesKHR);
   DEFINE_PROC(QueuePresentKHR);
   DEFINE_PROC(CreateAndroidSurfaceKHR);
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 #if OS_FUCHSIA
   DEFINE_PROC(ImportSemaphoreZirconHandleFUCHSIA);
   DEFINE_PROC(GetSemaphoreZirconHandleFUCHSIA);
diff --git a/vulkan/vulkan_swapchain.h b/vulkan/vulkan_swapchain.h
index 9c8fc6717e9d8..b617b659d04fb 100644
--- a/vulkan/vulkan_swapchain.h
+++ b/vulkan/vulkan_swapchain.h
@@ -60,7 +60,7 @@ class VulkanSwapchain {
 
   SkISize GetSize() const;
 
-#if OS_ANDROID
+#if FML_OS_ANDROID
  private:
   const VulkanProcTable& vk;
   const VulkanDevice& device_;
@@ -90,7 +90,7 @@ class VulkanSwapchain {
                                      sk_sp<SkColorSpace> color_space) const;
 
   VulkanBackbuffer* GetNextBackbuffer();
-#endif  // OS_ANDROID
+#endif  // FML_OS_ANDROID
 
   FML_DISALLOW_COPY_AND_ASSIGN(VulkanSwapchain);
 };